Laboratory experiments were carried out to study the effect of milling methods on the infestation of Sitophilus oryzae on stored rice grains during 2016-17. The results of the present investigation reveals that rubber milled rice were more preferred by the weevils than the iron milled rice with significant differences in weight loss existing among the various rice categories and the highest weight loss per cent was registered from SBA rice category (31.26±0.60 and 33.07±0.62) and the lowest from SMNA rice category (24.47±0.55 and 25.98±0.56) in 2016 and 2017 respectively. The highest damaged grain percentage was also registered from SBA rice category with 42.58±0.48% and 41.22±0.42% in 2016 and 2017 respectively.
Int.J.Curr.Microbiol.App.Sci (2020) 9(8): 880-886 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume Number (2020) Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2020.908.095 Effect of Milling Methods on the Infestation of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on Stored Rice Grains in Terai Agro-Ecology of West Bengal Supriya Okram* and T K Hath Department of Agricultural Entomology, Uttar Banga Krishi Vishwavidyalaya, UBKV, Pundibari, West Bengal, India *Corresponding author ABSTRACT Keywords Sitophilus oryzae, Rice, Milling methods, Iron milling, Rubber milling Article Info Accepted: 10 July 2020 Available Online: 10 August 2020 Laboratory experiments were carried out to study the effect of milling methods on the infestation of Sitophilus oryzae on stored rice grains during 2016-17 The results of the present investigation reveals that rubber milled rice were more preferred by the weevils than the iron milled rice with significant differences in weight loss existing among the various rice categories and the highest weight loss per cent was registered from SBA rice category (31.26±0.60 and 33.07±0.62) and the lowest from SMNA rice category (24.47±0.55 and 25.98±0.56) in 2016 and 2017 respectively The highest damaged grain percentage was also registered from SBA rice category with 42.58±0.48% and 41.22±0.42% in 2016 and 2017 respectively The two milling method also had notable impact on the adult population of S oryzae produced from the stored grain at 90 DAS It was observed that the adult population from rubber milled rice was significantly higher (330.17±5.31 and 340.50±5.44) than the population recorded from the iron milled rice (264.18±5.31 and 274.74±5.44) in both the experimental years of studies i.e., 2016 and 2017 The carbohydrates and protein content so obtained from the present studies were also noted to be one of the main factors to contribute to the preference of the rice weevils in which rubber milled rice (having 55.55±0.67% and 11.05±0.15% carbohydrate and protein respectively) had greater quantity of these as compared to the iron milled rice (49.74±0.67% and 9.09±0.15% carbohydrate and protein respectively) efficiency ratio owing to the presence of higher concentration (~4%) of lysine (Oko et al., 2012) The process of removal of hulls and brans from paddy grains to produce polished rice is termed as the rice milling The effect of the milling process on the outcome of rice quality has been researched by examining the quality of the whitened rice product focusing on parameters such as degree of milling, transparency, whitening, and yield (Schramm, 2006) The brown rice Introduction Rice, Oryza sativa (Linn.) is an economically important crop and the most important staple foods for the world’s population More than 90% of the world’s rice is produced and consumed in Asia The rice grain consists of 75-80% starch, 12% water and only 7% protein with a full complement of amino acids Its protein is highly digestible with excellent biological values and protein 880 Int.J.Curr.Microbiol.App.Sci (2020) 9(8): 880-886 contains more protein, minerals, and vitamins as compared to the milled rice or the white rice (Jones et al., 1946) FAO (1954) reported that the milled or white rice is more attractive in appearance, requires less time to cook, and keeps better in storage than the brown rice but in humid environments both easily become rancid It was observed that the protein content of rough, brown, and milled rice varied significantly among varieties where the Asian rice varieties were generally of lower protein content than those varieties planted in the United States and also difference of about 4% in protein content of the same variety of rice planted at different seasons was observed Juliano et al., (1964) Both the white and brown rice are susceptible to the rice weevil, S oryzae as the adults feed on rice and the larva develops inside the rice kernel (Arbogast, 1991 and Beckett et al., 1994) rice weevil were taken up to 90 days at weekly intervals The population build up of the adult weevil was also recorded after 90 days of storage Different physiological parameters like moisture percentage, length, breadth, 1000 grain weight, 100 grain volume and 100 grain density of the rice grains of each of the germplasm were also determined Likewise the biochemical parameters viz., proteins and carbohydrates were also determined Results and Discussion The present studies were to see the effects of milling methods of rice on the infestation of Sitophilus oryzae (L.) where two milling methods were adopted Firstly, iron milling in which all or part of the bran and germ from the rough rice/paddy was removed and the milled rice so obtained are also called as white rice And secondly the rubber milling by using the palm husker where the least processed form of rice was done by removing only the outer hull but the bran layers and the germ still retains and the rice produced from this milling method is also called as brown rice Materials and Methods The study was conducted in the Department of Agricultural Entomology of the varsity located at Pundibari, Coochbehar, West Bengal (India) during 2016 and 2017 For conducting this experiment all the paddy germplasms were milled by adopting different milling methods viz., iron milling and the another method by using the rubber huller namely “Palm Husker” However, both white and brown rice are susceptible to the rice weevil as the adults feed on rice and the larva develops inside the rice kernel (Arbogast, 1991; Beckett et al., 1994) As per Poonam Dhankhar (2004) milling is a crucial step in post-production of rice where the basic objective is to remove the husk and the bran layers from paddy grains and to produce polished rice which is edible and white rice kernel free of impurities The rice grains thus obtained after milling were sterilized under UV rays for 30 minutes in order to kill all existing insects or eggs or pathogens After the sterilization, grains of each germplasm weighing 50 gm containing only the sound, unaffected grains were kept in plastic bottle of 250 gm capacity Later ten pairs (male female ratio of 1:1) of five days old weevils were introduced in each bottle and tops were kept covered with muslin cloth and tightly fixed with rubber band to provide proper aeration The observations on different parameters viz., percent of damage grains and grain weight loss to different germplasms by The rice produced from these two different milling methods greatly influenced the infestation level of Sitophilus oryzae and the results of the present investigation reveals that irrespective of the rice categories rubber milled rice was more preferred by the weevils to the iron milled rice in both the years of studies as shown in table numbers 1, and 881 Int.J.Curr.Microbiol.App.Sci (2020) 9(8): 880-886 Table.1 Impact of milling methods on the percentage of grain weight loss of different rice categories due to S oryzae in summer and winter season during 2016 and 2017 Categories Medium aromatic Medium non aromatic Short bold aromatic Short bold non aromatic Short medium aromatic Short medium non aromatic Probability Milling Iron Rubber Probability CV (%) Summer (34.00±1.59)ab (32.95±0.71)ab 2016 Winter Pooled (25.15±2.18)ab (29.58±1.35)ab (23.21±0.98)ab (28.08±0.60)bc Summer (36.17±1.66)ab (35.06±0.74)ab 2017 Winter (26.22±2.20)ab (24.56±0.99)ab Pooled (31.19±1.38)ab (29.81±0.62)bc (35.66±0.71)a (26.85±0.98)a (37.92±0.74)a (28.22±0.99)a (33.07±0.62)a (34.24±0.75)ab (25.29±1.03)ab (29.77±0.64)ab (36.33±0.78)ab (26.52±1.04)ab (31.42±0.65)ab (31.58±0.85)bc (21.69±1.17)bc (26.63±0.72)cd (33.48±0.89)bc (22.77±1.18)bc (28.13±0.74)cd (29.69±0.65)c (19.24±0.89)c (24.47±0.55)d (31.60±0.68)c (20.36±0.90)c (25.98±0.56)d